Control Of Extracellular Fluid

Question 1

Na+ regulation responds primarily to changes in _____________

Answer 1

Blood volume

Question 2

Water regulation responds to changes in _________ and _________ of ECF

Answer 2

Osmolarity

Volume

Question 3

Na+ retention entails loss of ____

Answer 3

K+

Question 4

What are the 2 ways that aldosterone can be activated/

Answer 4

1. Angiotensin II
2. K+ plasma concentrations increase (remember that aldosterone will stimulate Na+ reabsorption, which will entail K+ loss)

Question 5

Aldosterone binds to the intracellular _______________ receptor in __________ cells

Answer 5

Mineralocorticoid

Principal

Question 6

What does spironolactone do?

Answer 6

Binds to the mineralocorticoid receptor and prevents aldosterone from having an effect

Question 7

What are the effects of aldosterone?

Answer 7

It stimulates transcription, resulting in up-regulation of:
Apical ENaCs

apical K+ channels

Na+,K+ ATPase

Mitochondrial metabolism

H+ ATPase

Question 8

What are the effects of angiotensin II?

Answer 8

Vasoconstrictor

Activates aldosterone

Stimulates Na+/H+ exchange in proximal tubule (NHE antiport)

Makes you thirsty

Overall- salt retention and elevation of BP

Question 9

What is a dipsogen?

Answer 9

Stimulates thirst

Question 10

What hormone regulates the levels of Angiotensin II?

Answer 10

Renin

Question 11

What cells release renin?

Answer 11

Granular cells (aka juxtaglomerular cells)

Question 12

What 3 mechanisms can stimulate renin release?

Answer 12

1. Intrarenal barorecpetors in the granular cells of JGA respond to stretch in afferent arterioles (Low BP=HiGh renin release)
2. Macula Densa senses flow to the distal tubule (NaCl levels) and will cause renin release if GFR is too low
3. Renal Sympathetic Nerves near granular cells will increase renin release via stimulation of β receptors

Question 13

How does renin release lead to angiotensin II floating around?

Answer 13

Renin cleaves angiotensinogen floating around in the blood to make angiotensin I, and then the whole ACE to angiotensin II thing

Question 14

Where does atrial natriuretic peptide come from?

Answer 14

Atria of the heart

Question 15

When do the atria release ANP?

Answer 15

When BP is high

Question 16

What effect does ANP have on the kidney?

Answer 16

1. Increases GFR

2. Decreases NaCl reabsorption by the CD

Question 17

How does ANP increase GFR (and thus, the filtered load of NaCl)?

Answer 17

Dilates the afferent arteriole and constricts the efferent arteriole

Question 18

How does ANP decrease NaCl reabsorption by the Collecting Duct?

Answer 18

1. Directly inhibits secretion of renin and aldosterone

2. Directly inhibits Na+ uptake by medullary CD

Question 19

What is the most important hormone regulating water balance?

Answer 19

ADH

Question 20

Where does ADH come from?

Answer 20

Pituitary gland

Question 21

What cauwses the release of ADH from the pituitary ?

Answer 21

Increased plasma osmolality

Plasma volume decreases

Question 22

Does ADH have an effect on NaCl excretion?

Answer 22

Very little

Question 23

Which is the primary controller of ADH release: plasma osmolality or plasma volume

Answer 23

Plasma osmolality

Question 24

What is the average osmolarity of the body?

Answer 24

290 mOsm/L

Question 25

If your plasma volume changes just a little, will ADH get released?

Answer 25

No you need a pretty significant loss of plasma volume (about 10%)

Question 26

Will a teeny tiny change in plasma osmolarity cause release of ADH?

Answer 26

Yes

Question 27

If you drink a ton of water will you release ADH?

Answer 27

No, and the collecting duct permeability to H2O will be diminished, so you will lose H2O in your pee

Question 28

How could a decrease in plasma volume lead to an indirect release of ADH?

Answer 28

SNS detects lower plasma volume-> SNS activity-> renin secretion -> aldosterone -> renal sodium conservation -> increased plasma osmolarity -> ADH release

Question 29

If you drink a ton of water, your urine volume will increase. Will you also be peeing out a lot of solutes?

Answer 29

No, the amount of solute excretion will remain relatively constant

Question 30

What is clearance?

Answer 30

The ml/min of blood plasma cleared of a given substance

Question 31

What is Osmolar Clearance?

Answer 31

The ml/min of blood plasma cleared of osmotically active particles

Question 32

How do you calculate osmolar clearance?

Answer 32

(Uosm)(V) _____________ Posm Uosm = osmolarity of Urine Posm- osmolarity of plasma

Question 33

What is a normal Osmolar clearance?

Answer 33

1-2 ml/min

Question 34

What does it mean if your Cosm (osmolar clearance) decreases?

Answer 34

You are not getting rid of enough solutes -POSITIVE osmolar balance = gaining osmoles and water and progressing towards edema

Question 35

What can cause a reduced Cosm?

Answer 35

Decreased GFR Increased Aldosterone (inapp. Reabsorption of sodium) Kidney disease that decreases kidney’s ability to eliminate solute

Question 36

If someone develops edema, do you think their Cosm went up or down?

Answer 36

Down. Reduced Cosm= not getting rid of enough solutes

Question 37

What effect will diuretics have on Cosm?

Answer 37

Increased. Will cause you to “dump” osmolytes and ECF will decrease

Question 38

What kinds of things can cause an increased Cosm?

Answer 38

Diuretics Reduced aldosterone Kidney disease that prevent normal reabsorption